This invention relates generally to ball-type control assemblies and devices for controlling the position of a cursor or the like over the field of a video display. More specifically, this invention relates to an improved and relatively simplified ball-type cursor control assembly, particularly of the type for use with video arcade games and the like, wherein the assembly includes improved force coupling between the control ball and position-responsive signalling devices.
Ball-type cursor control assemblies are well known for use with video displays, such as electronic tracking equipment, arcade games, and the like. Such ball-type cursor control assemblies typically includes a relatively freely rotatable control ball supported for rolling movement in frictional engagement with two or more traction devices in the form of wheels, shafts, and the like to rotate said traction devices about horizontal axes in response to rolling movement of the control ball. These traction devices are in turn coupled to appropriate signal generation components which provide electrical output signals for controlling the position of the cursor within the field of the video display, typically in terms of Cartesian coordinates. These signal generation components may take a variety of known forms, such as, for example, adjustable potentiometers as disclosed in U.S. Pat. Nos. 3,541,541 and 3,835,464, or a generator device as disclosed in U.S. Pat. No. 3,267,755, or light signal devices as described in U.S. Pat. Nos. 3,541,521 and 3,304,434.
In general, in a ball-type cursor control assembly, it is desirable to position the traction devices for contact with the control ball substantially at the horizonal equator or centerline of the ball thereby permitting adjustment of the cursor position along one Cartesian axis without alteration in the cursor position along the other axis. Moreover, such positioning of the traction devices has been found to substantially optimize force transfer between the control ball and the traction devices without slippage as a result of the directional force vectors acting therebetween. However, when the traction devices contact the horizontal equator of the ball, the traction devices are incapable of vertically supporting the ball. Instead, some additional support structure is required, as disclosed by way of example in U.S. Pat. Nos. 3,835,464; 3,625,083; and 3,269,190, which inreases the number of components in the control assembly and thus also increases the cost of the control assembly. In addition, the added support structure tends to increase frictional resistance to ball rotation wherein this increased friction can result in undesired ball slippage or require the use of relatively expensive yet low friction signal generation components, such as light signal devices, in lieu of less expensive but higher friction components, such as adjustable potentiometers.
Alternative control ball support techniques have been proposed to eliminate the additional support structure below the control ball by supporting the ball upon three or more rolling surfaces contacting the ball at points sufficiently below the horizontal ball equator, wherein two of these rolling surfaces comprise a pair of traction devices and a third rolling surface typically comprises a rolling bearing. Positioning these rolling surfaces below the horizontal ball equator advantageously permits these surfaces to lie on a radius sufficiently smaller than the ball radius to provide vertical support for the ball. However, in the past, downward forces applied to the control ball during use have tended to spread slightly the three rolling surfaces whereby such surfaces have been required to be positioned substantially below the horizontal ball equator where rotation of the ball in any direction necessarily results in at least some rotation of both traction devices thereby making it impossible to move the cursor accurately along one Cartesian axis.
There exists, therefore, a significant need for an improved ball-type cursor control assembly having rotatable traction devices positioned for contacting and vertically supporting a control ball at points substantially at the horizontal ball equator, wherein the control assembly does not require additional support structures positioned below the control ball. The present invention fulfills this need and provides further related advantages.